56 Journal of Agriculture, Victoria. [10 Jan., 1912. 



proportions of its constituents. Several copper soap formulae are recom- 

 mended in standard French works. Only certain kinds of soap are 

 suitable; with others, the gain in wetting power is either insufficient, or 

 counterbalanced by loss in adherence. 



A kind of mucilage known as Saponine appears to possess, in a high 

 degree, the power of reducing surface tension without the drawbacks of the 

 majority of soaps. The usual source from which it is obtained is the 

 powdered bark of certain plants such as Quillaia, Saponaria, &c., and 

 these have been successfully tried for the purpose. Quite recently, the 

 powdered fruit of Sapindus utilis, the Soap Tree, has been recommended 

 for the same purpose.* Used in the proportion of 2 per 1,000 of the 

 spraying liquid, it very considerably increases its wetting power, without 

 exerting any chemical action on the copper compounds contained in it. 



Other Conditions. 



Solubility conditions seem to be fulfilled by all the sprays in common 

 use. 



Adherence is, perhaps, the most important property of all, especially 

 when dealing with severe visitations. It stands to reason that, the better 

 the deposit adheres to the foliage, the longer will its protective action be 

 felt and the less often will it need to be repeated. If adherence be satis- 

 factory, it will require heavy rain to wash it off, whilst if it be faulty it 

 will be removed by a few light showers. The more recently a mixture has 

 been prepared, and the cooler it has been kept, the better it will adhere. 

 This applies particularly to copper-soda which deterioraties very rapidly, 

 especially if the weather be warmf. Copper-soda deteriorates much more 

 rapidly in this way than copper-lime (Bordeaux) or copper-potash ; the 

 latter, strange to say, is not at all generally used. In order to increase 

 adherence, several substances are added to mixtures. We may mention 

 the following : — Soap, rosin, sugar or molasses, linseed oil, and gelatine. 

 Some of these will be referred to later. 



As regards percentage of copper, though various strengths have been 

 recommended at different times, practical men now seem to be agreed, 

 after long years of experience, that ij to 2 per cent, is most satisfactory; 

 2 per cent, is the most usual strength — anything over this is unnecessary.! 

 These percentages are estimated as sulphate of copper, or its equivalent, if 

 other copper compounds of copper be employed. 



Convenience of preparation is of great practical importance. It is 

 mainly on this account that several of the newer preparations are gradually 

 displacing Bordeaux mixture in spite of their higher price. Most of these 

 innovations require to be merely mixed with the proper quantity of water 

 immediately before use. Their freedom from grit or lumps of any kind 

 obviates trouble through the clogging of nozzles, so frequent with badly 

 prepared Bordeaux. 



It is, of course, impossible to deal here with more than a few of the 

 many spray formulae now in use in France. It will suffice to refer briefly 

 to the way in which Bordeaux is prepared and to those of the newer sub- 

 stitutes which appear to have most to recommend them. 



{To be continued.) 



* G. Gastine. Revue de Viticvlture, Ath May, 1911, p. S'i.'i. This tree, which is somewhat extensively 

 grown in Alsreria, would do well in Northern Virtoria. Its value for increasinsr the efficiency of spraying 

 mixtures alone would justify its introduction to Victoria. 



t .T. M. Guillon and G. Gouirand, Revue de Viticulture, Vol. XI., p. 29. 



X This applies to France. In the moist climate of Switzerland, where downy mildew is very virulent, 

 anything less than 2 per cent, is considered insufficient, whilst sprays containing; up to 3 per cent, copper 

 sulphate" are often used. 



